Wave transmission lines and networks – Resonators – With tuning
Patent
1996-06-04
1997-10-14
Lee, Benny
Wave transmission lines and networks
Resonators
With tuning
3332191, H01P 710
Patent
active
056776543
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/Fl95/00544, filed Oct. 4, 1995 published as WO96/11508 Apr. 18, 1996.
BACKGROUND OF THE INVENTION
The invention relates to a dielectric resonator comprising a dielectric cylindrical resonator disc, a frequency controller comprising an adjustment mechanism and a dielectric cylindrical adjustment disc, one of two opposite planar surfaces of the adjustment disc being arranged against one of planar surfaces of the resonator disc so that the adjustment disc is movable by means of the adjustment mechanism in the radial direction with respect to the resonator disc for adjusting the resonance frequency of the resonator, and an electrically conductive casing.
Recently, so-called dielectric resonators have become more and more interesting in high frequency and microwave range resonator structures, as they provide the following advantages over conventional resonator structures: smaller circuit sizes, higher degree of integration, improved performance and lower manufacturing costs. Any object which has a simple geometric shape, and the material of which exhibits low dielectric losses and a high relative dielectric constant may function as a dielectric resonator having a high Q value. For reasons related to manufacturing technique, a dielectric resonator is usually of cylindrical shape, such as a cylindrical disc.
The structure and operation of dielectric resonators are disclosed e.g. in the following articles: Siemens Components XXIV (1989) No. 5, p. 180-183. Journal, September 1986, p. 189--189. Microwave Circuits", Marian W. Pospieszalski, IEEE Transactions on Microwave Theory and Techniques, VOL. MTT-27, NO. 3, March 1979, p. 233-238.
The resonance frequency of a dielectric resonator is primarily determined by the dimensions of the resonator body. Another factor that has an effect on the resonance frequency is the environment of the resonator. By bringing a metallic or any other conductive surface to the vicinity of the resonator, it is possible to intentionally affect the electric or magnetic field of the resonator, and thus the resonance frequency. In a typical method for controlling the resonance frequency of the resonator, the distance of a conductive metallic surface from the planar surface of the resonator is adjusted. The resonance frequency changes as a non-linear function of the adjusted distance. Due to this non-linearity and the abrupt slope of adjustment, accurate control of the resonance frequency is difficult and demands great precision, particularly at the upper end of the control range. In addition, an unloaded Q value varies as a function of the distance of the conductive plane.
It is possible to maintain the Q value on a constant level, and achieve a more linear frequency control in a wider range by bringing, instead of a conductive tuning plane, another dielectric body to the vicinity of the resonator body. In this case, too, the slope of adjustment is still steep.
One dielectric filter design of this kind is known from Finnish Patent Application 912256. In this prior art resonator, an apparently integral resonator is composed of two dielectric discs set against each other, so that a radial movement of the discs with respect to each other changes the shape of the resonator, whereby changes in the normal field patterns of the electric and magnetic fields cause a change of the resonance frequency. Thus, a relatively linear and a less steep control curve of the resonance frequency is achieved, while maintaining a high and consistent unloaded Q value of the resonator during the adjustment.
In this prior art resonator as well, frequency control is based on a highly accurate mechanic movement, in addition to which the slope of adjustment is still very steep. As the resonance frequency becomes higher, e.g. to the range 1500-2000 MHz or higher, the dimensions of the basic elements of the dielectric filter, such as dielectric discs or adjustment mechanisms are reduced. As a result, adjusting the resonance frequency of a dielectric resonat
REFERENCES:
patent: 4849722 (1989-07-01), Cruchon et al.
patent: 5315274 (1994-05-01), Sarkka
patent: 5352997 (1994-10-01), Sarkka 333219.1
Lee Benny
Nokia Telecommunications Oy
Summons Barbara
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